1. Field of the Invention
The invention relates to full line type inkjet printing apparatuses, and in particular to inkjet printing apparatuses that detect the ejection state of ink ejected from the ejection ports of a print head.
2. Description of the Related Art
Inkjet type printing apparatuses are known in the art. Such inkjet printing apparatuses form characters and images by ejecting ink from ejection ports and fixing it onto a print medium. Among inkjet printing apparatuses, full line type inkjet printing apparatuses have been employed in recent years, which have a print head provided with an ejection port array corresponding to the printing width, and perform printing while conveying the print medium. Full line type inkjet printing apparatuses are becoming wider in use because of their ability to speedup printing. With respect to such full line type inkjet printing apparatuses, there are apparatuses that perform margined printing, in which printing is performed while establishing a margin along the edges of the print medium (the edges along the widthwise direction), and marginless printing, in which printing is performed without establishing a margin.
There are times where, for various reasons, the ejection of ink from an ejection port is in an unsatisfactory state. In the case where the ejection of ink is in an unsatisfactory state, there are times when it is necessary to perform measures such as to stop ink ejection from the ejection port and instead eject ink from a separate ejection port. As such times it is necessary to detect the position of the ejection port having an unsatisfactory ejection state.
As a method for detecting detection ports having an unsatisfactory ink ejection state, a method is known wherein a test pattern is printed on the print medium and ejection ports having an unsatisfactory ink ejection state are detected from the test pattern image. For example, a full line type inkjet printing apparatus, in which a print head is capable of performing printing across the entire widthwise direction of the print medium, and having a printing means for performing printing on the printing medium and a sensor for reading a printed test pattern, is disclosed in Japanese Patent Application Laid-Open No. 2006-205742. By way of the test pattern being read by a sensor, in the case where an ejection port having an unsatisfactory ejection state occurs on the print head, it is possible to detect the ejection port having an unsatisfactory ejection state by way of the test pattern being detected. In particular, in Japanese Laid-Open Publication No. 2006-205742, in the case where a marginless printing is performed that carries out printing such that a margin is not generated at the outer ends of the print medium (the outer ends in the width direction), ejection ports having an unsatisfactory ink ejection state are detected by way of the test pattern being detected. As for the inkjet printing apparatus disclosed in Japanese Laid-Open Publication No. 2006-205742, in the case where marginless printing is performed, ejection ports having an unsatisfactory ink ejection stare are detected by using a test pattern that is printed such as to cross the entire width of the print medium.
In the case where a marginless printing is performed, the printed image is formed longer than the print medium in the widthwise direction of the print medium, such as to run off of the edge of the print medium. On the other hand, in the case where a margined printing is performed, the printed image is printed on a portion of the print medium such as to reside within the print medium along its widthwise direction. Because of this, a portion of the ejection ports that are used when performing a marginless printing occur that are not used in the case of performing margined printing. Thus the region of used nozzles on the print head differs between the case where printing is performed by a margined printing and the case where printing is performed by a marginless printing. Because of this, the necessary test pattern region differs between the case where margined printing is performed and the case where marginless printing is performed, when printing a test pattern and detecting ejection ports having an unsatisfactory ejection state, from the test pattern. In this manner, in inkjet printing apparatuses capable of performing margined printing and marginless printing, the detection region on the test pattern, at the time of performing the detection of ejection ports having an unsatisfactory ink ejection state from the test pattern, is unfixed.
When the ejection ports used when printing a test pattern have been made to correspond to the ejection ports used in margined printing, when a marginless printing is performed there are times where ejection ports occur, at a section of the ejection ports within the print head, at which it is not possible to detect whether the ink ejection state is satisfactory. And when the ejection ports used when printing a test pattern have been made to correspond to the ejection ports used in marginless printing, when a margined printing is performed there are times where it is not possible to detect whether the ink ejection state is satisfactory, with respect to the ejection ports that are not used in printing. Because of this it is not possible to establish the range of ejection ports, within the print head, which should be set as the region at which detection of whether the ink ejection state is satisfactory is performed.